Orange rust

About

A rust disease of blackberries and black and purple raspberries that infects the whole plant, roots and all, for life. Red raspberries do not get it.

Also called orange rust

How to recognize it

Symptoms

In spring, new shoots come up weak and spindly with small, narrow, pale yellow-green leaves. Within 2 to 3 weeks the leaf undersides are covered with waxy blisters that burst into bright orange powder. Infected plants rarely flower and give little or no fruit.

Worse when

Cool, moist weather; leaves must stay wet for many hours for spores to infect.

How it spreads

The fungus lives inside the crown and roots year-round, and wind carries the orange spores to healthy plants, including from wild brambles.

When

Orange spores show in spring on new shoots, sometimes again in late summer.

What to do, gentlest first

Prevention works best; most sprays only protect healthy leaves and can't cure infected ones. Always read and follow the product label.

1. Start clean and remove wild brambles Prevent

   Buy disease-free plants, keep canes thinned and weeds down for airflow, and clear out wild blackberries and black raspberries nearby. Red raspberries are an option where orange rust is common.

2. Dig out infected plants, roots and all By hand

   Check plants in early spring when shoots are under a foot tall and dig up any with weak, pale shoots, including the roots, before the orange spores burst open. Do not wait for them to recover; they never do.

   Fungicides do not cure or control orange rust. UC IPM notes glyphosate or triclopyr can be spot-applied to kill infected plants, but these can injure nearby plants you want to keep; follow the label.

Plants it affects

Black raspberry (blackcap), Blackberry, Raspberry